Plants, Algae, CO2, and PH

This is my first mail to this list, so let me say that I've enjoyed reading 
what everyone has to say.  It's been very, very informative, though I'm 
certainly not going to say I understand all the chemical reactions you guys 
talk about...

Now the reason I'm posting: 

I have a well-planted 55-gallon community tank with about 20 fish (not counting 
the krib babies) and the following plants:  Hygrophila Polysperma, Crinum 
Thaianum, Echinodorus Maior, E. Amazonicus, E. Tenellus, a couple of Aponogeton 
Undulatus, Ludwigia Repens, Cryptocoryne Crispatula, C. Becketti, Water 
Wisteria (?), and one plant that I haven't ID'd.  There are two filters on the 
tank -  a Whisper on one end and a BioWheel on the other.  Lighting is two 33 
watt flourescents.  (I'm not sure of the brand.  The lighting fixture holds two 
48" T-8 bulbs, which are currently impossible to find in Atlanta, so I mail 
ordered them from some place in California.  It was the only place I could find 
that had 48" T-8's.)  These bulbs are on approximately 12 hours a day.  Also, 
at least 30% of the water is changed each week and a half.  

And I also have a big algae problem.  In fact, it's the algae from hell.  I'm 
99% sure it's the black brush algae pictured and discussed on page 166 (I 
think) of the Baensch Aquarium Atlas, Vol. 2.  This stuff just does not come 
off.  I have two large pieces of driftwood in the tank, and I've used a 
toothbrush on them to try to get this stuff off with no success.  Initially, it 
took over one piece of driftwood, then migrated to the second piece, and now 
it's started on the plants.  Just on the edges.  The Crinum has it fairly 
badly.  The E. Maior and E. Amazonicus are both looking pretty ragged.  It's 
also on the E. Tenellus and the Ludwigia Repens.   Obviously, I've got to get 
rid of this stuff or the plants are going to suffer more than they already 

I've tested nitrates and phosphates (Tetra kits), and both are low to 
non-existent.  I recently added Phos-Zorb filter media to the Whisper filter, 
hoping that the phosphate test was incorrect and that this might have an 
impact.   So far, no impact.  Algae eating fish don't seem to be the solution 
either - the pl*co, Siamese algae eater, and five Otocinclus don't touch this 

The Baensch atlas says adding CO2 is the solution to getting rid of this 
stuff.  Why?  Will adding CO2 increase the photosynthesis of the plants, 
thereby increasing their need for nutrients and cutting off that available to 
the algae?  Or does it just not flourish in a high CO2 environment?  And if the 
CO2 does have an effect, is it too late to save the leaves already infested 
with the algae?

I have a PH of around 6.2.  I began DIY CO2 injection over the Memorial Day 
weekend, so I suspect that it's now lower than that (the Tetra kit goes down to 
6.0).  I also included baking soda in the mix to try to buffer the PH 
somewhat.  The only CO2 kit I can find is a Tetra, and I've read that they 
aren't accurate, so I haven't tested CO2 concentration yet.  Using a Tetra KH 
test kit, the KH is non-existent as well (the solution is never blue, even with 
the first drop).

The CO2 airline is placed so that the bubbles enter the intake tube of the 
Biowheel.  You can actually see smaller bubbles of what I presume to be CO2 
coming out of the Biowheel.  The tank is stocked with mostly S.A. Cichlids, and 
they don't seem to be too bothered by the PH drop associated with CO2 
injection.  I can see what I hope to be O2 on the leaves of some of the taller 
plants.  The low growing plants don't have this, however.  And the O2 or 
whatever is not streaming to the surface as I've imagined truly healthy and 
happy plants with CO2 injection would do - it's just on the leaves.

Since I began CO2, the algae has turned a lighter shade of green (please tell 
me it's dying).  The Crinum, Hygro, E. Maior, Ludwigia, and Water Wisteria seem 
to be responding favorably growth-wise, but they still have the same amount of 
the algae on them.  The other plants, mainly low-growers, show no appreciable 
change.  On the other hand, the fish seem none the worse for wear and tear.

Any suggestions for killing this algae from hell and saving the plants would be 
most appreciated.  Also, any suggestions for improving the CO2 injection method 
would also be welcome.  I'm also interested in suggestions for stabilizing the 
PH at around 6.6.  Thanks in advance.


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